In pyrotechnic drives, in particular linear drives, which form part of a belt tensioner system, the problem exists that a higher drive power can not be achieved simply by more powerful propellant charges. This lies on the one hand in the limited mechanical loading capacity of all parts of the drive, for example of seals or of a piston rod. On the other hand, as was discovered, with too high an energy suddenly becoming free, a majority of this energy remains unused through deformation of parts of the drive.
From DE 44 15 373.2 it is known to provide two propellant charges which are separated from each other by a bursting membrane, the propellants of which have different deflagration rates and are ignited successively. Thereby, the peak loads to which the parts of the drive are exposed can be reduced and a smaller initial pressure rise can be achieved. In the known drive, the problem exists that owing to the encapsulating of the propellant charges one inside the other, owing to the principle only. a relatively small staggering in time is possible between the igniting and the burning up of the propellant charges. A portion of the gas which is produced on deflagration of the propellant associated with the first propellant charge, arrives into the space taken up by the second propellant charge and thereby relatively late at the outflow opening. In addition, the space taken up by the known drive is relatively large.